Inkjet image forming apparatuses, for example, inkjet printers, have become widely available because of their low running costs, ease of colorization of a print image and miniaturization, and the like. Inkjet printers record an image by discharging small amounts of ink from tiny ink discharge outlets extending through an ink discharge surface of a print head. If print operation has not been performed for a long period of time and thus ink has not been discharged from the ink discharge outlets of the print head for such a long period, ink deposited on the ink discharge outlets formed through the ink discharge surface and the adjacent areas in the previous print operation may have been vaporized, dried, solidified, and hardened. This makes it difficult to properly discharge ink.
Conventionally, therefore, print-head cleaning is performed by pressing a blade, such as a relatively hard rubber one, against an ink discharge surface of a print head, sliding the blade over the ink discharge surface, and removing (wiping) solidified and hardened ink that has been deposited on the ink discharge surface. Relating to this, a technique is disclosed in which wiping effects are further enhanced by rotating a plurality of blades mounted on a rotating shaft (see, for example, Japanese Unexamined Patent Application Publication No. 57-034969 (pp. 2 to 3 and FIGS. 3 and 4)).
However, in the technique described in Japanese Unexamined Patent Application Publication No. 57-034969, since blades formed of a relatively hard rubber or the like are pressed against an ink discharge surface of a print head and slid over the ink discharge surface to wipe off ink deposited on the ink discharge surface, the ink discharge surface may be damaged by being subjected to a strong force applied by the blades. Additionally, the technique using the blades described above depends solely on wiping effects, but only performing wiping may cause ink to remain in ink discharge outlets. If a plurality of blades are used in order to wipe a line print head, in which a large number of ink discharge nozzles are arranged so as to correspond to the full width in a print area, problems arise in which an ink discharge surface may be damaged and ink may remain in ink discharge outlets and the adjacent areas, as in the above case.
Relating to this, Japanese Patent Application No. 2002-192236 discloses a technique in which an ink discharge outlet is cleaned by preliminarily discharging ink droplets to a cap member of a print head at a time when an image forming operation begins. Since the capacity of the cap member to hold ink is limited, this technique has a problem in which the cap member must be handled as a consumable item and replaced with a new one multiple times. Furthermore, since an area (range) for preliminarily discharging ink to the cap member is limited, the cap member must be moved several times for performing necessary preliminary discharge, and therefore, a problem arises in which an actual print time period is increased. Additionally, when continuous printing is performed, since an operation of moving the cap member and other operation are included, a problem arises in which the actual print time period is increased correspondingly.